In power plant systems employing coal-fired steam generators it is known to employ various equipment to extract heat from the combustion gases leaving the steam generator and to employ various cleaning equipment to take the particulate matter and various undesirable gases out of the gas stream prior to discharging the same to atmosphere. One such system employs an air heater, an electrostatic precipitator and a wet scrubber with the electrostatic precipitator being downstream of the air heater in the direction of the combustion gas flow and with the wet scrubber in turn being downstream of the electrostatic precipitator. In such a system it is desirable that the temperature of the combustion gases exiting from the electrostatic precipitator and directed to the stack be at a predetermined minimum temperature in order that the gases will have a desired buoyancy and will, upon leaving the stack, continue to rise to a desired height. It is also desired that the gases exiting from the stack not have a plume of condensed vapor but that they be transparent such that the opacity of the gases can be monitored. Still another reason for maintaining a desired temperature of the gases as they enter the stack is to maintain condensation in the stack and the resulting deterioration of the stack at a minimum. Accordingly, various schemes for elevating the temperature of the gases leaving the scrubber have been suggested.